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Focus Interactive Vehicle Dynamics provide added driving reassurance
The Ford Focus interactive vehicle dynamics system – which is currently available as an option in Europe and will be offered to North American customers in future model years – provides an effective aid to safety in difficult driving conditions. The system continuously checks 150 times per second whether the behavior of the car is matching the steering input, using seven different vehicle sensors and two independent microprocessors. As soon as it detects the first signs of any deviation, it is designed to intervene to help restore stability, reducing the risk that the driver might lose control.
The system is an evolution of ABS and the traction control system (TCS). Like TCS, interactive vehicle dynamics uses the engine management controls to reduce power if there are signs that traction might be lost when entering a turn. It also has the capability of applying individual elements of the ABS braking system to initiate dynamic stabilizing countermeasures before the car starts to deviate from the driver’s chosen line.
The Ford Focus has been designed, developed and fine-tuned to deliver a class-leading combination of comfort, agility, precision and stability. It is a highly competent and dynamically reassuring vehicle to drive, whatever the weather conditions. Some situations – such as roads covered in snow or ice – make much higher demands on driving skills and, sometimes, present unexpected hazards that take even the most experienced driver by surprise. The interactive vehicle dynamics system is designed to reduce driver anxiety and driving stress through highly sophisticated electronic systems that help increase safety margins and decrease instability during a wide variety of maneuvers.
How the system works Focus’ interactive vehicle dynamics system uses the individual wheel speed-sensors of the ABS system in combination with three additional highly sophisticated sensors: one fitted around the steering column to monitor the driver’s inputs and two more mounted close to the center of gravity to detect vehicle responses.
Whenever the behavior of the car fails to match calibration data for the vehicle speed stored on a dynamic handling map in the on-board computer, stabilizing countermeasures are initiated.
The four wheel-speed sensors of the ABS/TCS system are supplemented by a yaw-rate sensor and a lateral-acceleration sensor located under the front passenger seat close to the center of gravity of the car. A sensor on the steering column assesses the driver’s input angle so the response to his input can be compared with a calibrated map of the known driving envelope.
To provide a fast-acting hydraulic pulse, a new brake booster with an electrical solenoid added to its operating rod is also included in the system. It allows line pressures of 130-180 bar to be generated in a few milliseconds. Pressure transducers are also added to the output from the brake master cylinder.
The key to this advanced system is the application of aerospace technology to provide the extremely sensitive yaw rate sensor. It uses a physics concept, similar to centrifugal force but acting only within a rotating object – known as the Coriolis effect – that was originally developed for navigational gyrocompasses and space rocket stabilization systems. It detects and measures tiny changes in angular vehicle velocity about its vertical axis when negotiating a turn, converting them to an electronic signal that is monitored by two independent microprocessors every seven milliseconds – equivalent to once every 4 inches of road covered at 30 mph.
In the early stages of dynamic stabilization, interactive vehicle dynamics uses the normal TCS system to reduce power via the engine management module and help prevent loss of traction as the car enters a slippery turn. If it then detects a tendency for the front of the car to drift towards the outside of the turn (understeer) and the limit of adhesion is approaching, the system applies a braking impulse to the inside rear wheel, inducing a self-stabilizing yaw moment that helps straighten the car to bring it back on line. If it detects a tendency for the tail to swing out instead (oversteer), a braking impulse is applied to the outside front wheel, with the same self-stabilizing effect.
In both instances, the system is designed to act well before the destabilizing forces take effect, in much the same way that ABS operates before the wheels lock under braking and TCS operates before the driver senses there is any loss of traction. Unlike these other systems, Focus’ interactive vehicle dynamics monitors the vehicle characteristics continuously and can even operate when the car is rolling freely without braking or driving torque. The whole system is fully integrated with ABS and TCS to provide smooth and seamless dynamic control of the vehicle.
Text Source: Ford Media Information Center
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